Abstract : Composite metals with both ferromagnetic and conductive layers are known to be more effective than monometals in attenuating electromagnetic fields at low and intermediate frequencies. Their usefulness, however, has been limited because available methods of analysis apply only to monometals and require different approximations in high and low frequency regions. This paper describes a method using the Schelkunoff surface and transfer impedance characteristics of the component layers to determine the shielding effectiveness of the composite. The procedure applies to both 'high' and 'low' frequency cases, and can be carried out with the aid of a programmable calculator. Laboratory measurements of shielding effectiveness of several monometals and composites, over a frequency range of 50 Hz to 500 KHz, indicated satisfactory agreement between predicted and measured values. It is believed that the impedance method will be of value in selecting optimal materials and dimensions for cable shields. (Author)